Long term evolution (LTE) and other radio communications technologies can require significant infrastructure and configuration. Generally, network operators test various aspects of their network equipment to ensure reliable and efficient operation. Network operators typically simulate various conditions before equipment is deployed in a live network to decrease avoidable delays and/or other problems.
Various technical specifications, such as the 3rd Generation Partnership Project (3GPP) Technical Specifications 36.211, 36.212, 36.213, and 36.214, hereinafter respectively referred to as “TS 36.211”, “TS 36.212”, “TS 36.213”, and “TS 36.214”, define aspects of LTE communications. Generally, data from the network to a user device is referred to as downlink data and data from the user device to the network is referred to as uplink data. For example, user equipment (UE), such as a cellular mobile phone, a laptop, other user device, may communicate with an enhanced or evolved Node B (eNode B), also referred to herein as a eNB, via the cellular radio transmission link. Data that is sent from the eNode B to the user device is downlink data, and data that is sent from the user device to the eNode B is uplink data.
LTE data is usually transmitted using one or more multiplexing and/or modulation schemes. For example, in some LTE networks, downlink data is transmitted using an orthogonal frequency-division multiplexing (OFDM) and uplink data is transmitted using single carrier frequency-division multiple access (SC-FDMA). Such schemes may allow multiple streams of data to be sent simultaneously (e.g., at different frequencies). While such schemes may allow data to be communicated at high-speed, significant processing is required to encode and decode the data.
In LTE networks, receipt of physical layer uplink data by an eNode B is confirmed using hybrid automatic rapid request (HARQ) feedback (e.g., HARQ indicator (HI) bit). The HARQ feedback is sent from the eNode B to the UE to acknowledge (ACK) or negatively acknowledge (NACK) the transmission. If the UE receives an ACK, there is no need to retransmit data to the eNode B. However, if the UE receives a NACK, the UE will retransmit the data.
If the UE incorrectly decodes or interprets an ACK as a NACK, the UE will erroneously retransmit data on an uplink channel that the eNode B is not expecting. This erroneous transmission can cause radio resource collisions with other UE transmissions. Similarly, the incorrect interpretation of a NACK as an ACK leads to no retransmission when a retransmission is expected. Such problems are magnified when multiple UEs are being simulated by a multiple UE (multi-UE) simulator.
According to 3GPP specifications, each UE maintains a number of parallel HARQ processes allowing transmissions to take place continuously while waiting for HARQ feedback on the successful or unsuccessful reception of previous transmissions. In our multi-UE simulator, it is desirable to support hundreds of UEs in one sector, and therefore scalability has to be addressed. It is critical to utilize the memory and computation resources efficiently so that a large number of UEs can be supported in real time.
Accordingly, in light of these difficulties, a need exists for improved methods, systems, and computer readable media for performing LTE HARQ processing.